1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device that can prevent light leakage from occurring.
2. Discussion of the Related Art
A liquid crystal display device is widely used in various fields of notebook computers, monitors, spacecraft, aircraft, and etc. owing to advantages of low power consumption based on a low driving voltage and portability.
The liquid crystal display device includes a lower substrate, an upper substrate, and a liquid crystal layer between the lower and upper substrates. In the liquid crystal display device, an alignment state of liquid crystal molecules is controlled based on whether or not an electric field is applied thereto, and light transmittance is controlled according to the alignment state of liquid crystal molecules, whereby images are displayed thereon.
Hereinafter, a related art liquid crystal display device will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view illustrating the related art liquid crystal display device.
The related art liquid crystal display device includes an upper substrate 10, a lower substrate 20, a column spacer 30, and a liquid crystal layer 40.
Black matrixes 12 are formed on the upper substrate 10, and a color filter 14 is formed between the black matrixes 12. An overcoat layer 16 is formed on the color filter 14, and an upper alignment film 18 is formed on the overcoat layer 16.
A device layer 22 including a thin film transistor, a pixel electrode, and a common electrode is formed on the lower substrate 20, and a lower alignment film 24 is formed on the device layer 22.
The column spacer 30 is formed between the upper substrate 10 and the lower substrate 20 to maintain a cell gap of the liquid crystal display device.
The liquid crystal layer 40 is formed between the upper substrate 10 and the lower substrate 20. The liquid crystal layer 40 is arranged depending on an alignment direction of the upper alignment film 18 and the lower alignment film 24 in a state that no electric field is applied between the pixel electrode and the common electrode. An alignment direction of the liquid crystal layer 40 is varied depending on an electric field direction in a state that an electric field is applied between the pixel electrode and the common electrode.
In the aforementioned related art liquid crystal display device, the upper alignment film 18 or the lower alignment film 24 is damaged by the column spacer 30, whereby the alignment direction of the liquid crystal layer 40 is varied. For this reason, a problem occurs in that light leakage is caused. This problem will now be described in more detail.
With the tendency of slimness of the liquid crystal display device, thicknesses of the upper substrate 10 and the lower substrate 20 have been gradually reduced. If the thicknesses of the upper substrate 10 and the lower substrate 20 are reduced, it is likely that the substrates get bent. If the substrates get bent, the column spacer 30 is pressurized and its position may be varied. In this case, the column spacer 30 may damage the upper alignment film 18 or the lower alignment film 24 while moving.
As described above, if the upper alignment film 18 or the lower alignment film 24 is damaged by the column spacer 30, an initial alignment direction of the liquid crystal layer 40 is varied at the damaged position. For this reason, light leakage occurs, whereby quality of the liquid crystal display device is deteriorated.